1. Field of the Invention
The present invention, in general, relates to a system for injecting grout into cracks that require sealing via access holes and, more particularly, to apparatus that receive chemically reactive grout components separately, combine the components within the access holes near the crack, and then, inject the resultant grout into the crack.
It is necessary to inject grout to seal cracks and crevices which occasionally develop in a variety of structures. For example concrete dams may settle and crack, sometimes leaking water through the cracks that develop. Similarly cracks occasionally form in other types of structures such as tunnels, pipes, conduits, and sewer lines, for example. These cracks may be either above or below grade level.
A variety of reasons contribute to crack formation including settling of the structure, earthquake, accident, and other causes. In some cases, as hereinbefore mentioned, the cracks will leak water or other types of fluids therein and will therefore require timely repair. A crack or crevice through which there is a leakage of fluid is referred to as having a "pervasive flow" occurring therein. In other cases a leakage does not occur, yet the crack must nevertheless be repaired to prevent further deterioration of the structure from occurring.
Occasionally the cracks afford easy access and grout application is a task that is easily accomplished. Often though the cracks are difficult to access and require drilling long holes and injecting grout through the drilled holes.
The term "long hole" is used in favor of the term "deep hole" because sometimes the holes that are drilled in order to provide access to the cracks and crevices are indeed long, but not necessarily "deep" nor are the bored holes always in a direction that extends below the drilling equipment. It is necessary to drill at a variety of angles with respect to the drilling surface including drilling horizontally, down at some predetermined angle, or even in an upwards direction in order to access the crack that has formed. These types of drilled holes are often long but are not necessarily deep.
The difficulty with injecting grout into long holes is due simply to the fast reacting, and therefore also, the generally fast setting nature that is required of the two part (binary) chemical grouts that are, at present, commonly used for such purposes.
The most common of the binary chemical grouts that are used fall into one of the two general classifications of grouts, either monomers or polymers. Examples of monomer based grouts include the acrylamides, acrylates, and acrylics. A common example of a polymer grout is polyurethane. The polyurethanes are often referred to as simply the "urethanes" and include many of the preferred types of grouts that are used. Other types of binary chemical grouts not listed herein are sometimes appropriate for certain types of repair.
There are many "systems" for each of these grout families, each system usually referring to some particular characteristic of the cured grout. Examples of some systems include "gel", "flexible foam", "hard foam", and "solid" systems.
Certain repair situations respond better when certain types of grout systems are used. For example a solid grout system may be suitable for use to effect repairs when no further motion by the structure is anticipated. If continued motion by the structure is anticipated to occur, then repair may best be accomplished by the use of a gel or perhaps a flexible foam grout system.
Regardless of the grout system selected, all of the binary grouts are broadly defined to be any two part material that can be made to flow, usually by means of a pump, before the grout has had time to set or to cure. The terms "set" and "cure" are used interchangeably.
Each binary chemical grout formulation has one principle component part that is referred to as the "resin" and a second principle component part that is referred to as the "catalyst". The catalyst that is used for many of the preferred grouts is water (H2O). For certain binary grouts other chemicals may be combined with either the resin or the catalyst just prior to use. These chemicals are referred to as "additives" and they are used to modify some characteristic of the grout being used. For example certain additives are used to either lengthen or shorten the "setting" time of a grout.
For all types of binary chemical grouts when the catalyst component is blended with the resin component, a chemical reaction immediately begins to occur whereby a grout is formed. The process of blending the catalyst with the resin is often referred to as "reacting" the components. For many of the chemical grouts listed, a durable and expansive fast setting grout is thereby formed that is well suited for sealing these types of cracks and crevices.
Furthermore, it is not a practical option to attempt to slow reactant times while still preserving the fast setting time that is required. A slow reactant time (which would provide a longer time to set) is especially ill suited when injecting grout into formations having a pervasive flow occurring therein. The flow would tend to carry a slow reactant grout away before it had sufficient time to set and to adhere to its surroundings, thereby preventing an effective sealing of the crack from occurring. This type of situation is often encountered when sealing cracks that occur in water dam structures, for example.
It is also the case where "freezing sand" is a requirement. Freezing sand is an expression which originates from an industry practice whereby coolant is used literally to freeze sediments in position thereby permitting the accomplishment of some other task which requires a rigid formation. It is also currently used in industry to refer, generally, to the immobilization of sediments. In particular as used hereinbelow, freezing sand refers to the immobilization of sand, silt, and other sediments in position by means other than by merely a lowering of the temperature thereof.
Occasionally water dams and other structures develop a flow, usually by water, that is occurring underneath a portion of the reinforced dam structure or foundation. The reinforced portion of the dam structure may be constructed of concrete or of other materials. In this instance, water finds a path whereby it begins to flow underneath the reinforced portion of the structure. As the water flows it is constantly eroding more of the sand, silt, and other materials away from underneath the structure which in turn is enlarging the pathway under the structure, increasing the water flow rate, weakening the supporting base, and for as long as it continues, ever worsening and compounding the problem.
The necessary repair procedure in such a situation is to "freeze the sands" underneath the structure and it is in general quite similar to the required procedure for long hole crack repair having a pervasive flow occurring therein. A two part fast setting grout is reacted and is then injected onto the sand, silt, and other materials that are located underneath the reinforced portion of the structure where the leak is occurring thereby intersecting the flow of water. The fast setting grout mingles with the sand and silt and other materials and solidifies these materials into a unitized mass together with the grout.
A fortified and reinforced means of sealing the leak and also of preventing further erosion from occurring is thereby achieved. The result of this process is to "freeze the sands" that are located underneath the structure. A slow setting grout would in this instance also be removed and carried away by the pervasive flow before it had sufficient time to adhere to the sands and silt, thereby once again preventing an effective repair from occurring.
The hereinbefore described repair situations require that the preferred two part grout formulations, of necessity, have a short setting time. However if a grout formulation having a short setting time is reacted (mixed) at or near the drilling surface and is then piped through long holes to reach either a crack in the structure or a leak that is located underneath the structure, it will actually begin setting prior to reaching the repair area.
Consequently after the grout begins to set, its viscosity increases greatly so that it will no longer flow easily through the conduit that is used to transport the grout nor will it flow properly into the cracks and crevices that require sealing. Furthermore, once it begins to set it will no longer be capable of achieving an optimum bond with the materials surrounding the crack or the crevice. After a reacted grout begins to set, its efficacy at sealing cracks and crevices or of "freezing sand" is greatly diminished.
While a two part urethane grout is described as one of the presently preferred grout formations, other present and future grout formulations will also have to be fast setting for the same reasons as described hereinbefore. It does not matter if the grout formulation requires the mixing together of two or more component parts, to be effective at freezing sand and at sealing cracks in the presence of a pervasive flow, the grout, after having been reacted, must be fast setting. Any fast setting grout will in turn be difficult to pump through long holes and will also experience diminished repair efficacy if it is reacted too early prior to injection into the crack or onto the sands and silt to be frozen.
Accordingly there exists today a need for a long hole chemical grout injector system that is able to react the grout components in ideal proximity with respect to the crack that is being sealed or with respect to the sands and silts to be frozen. Clearly, an apparatus which allows for the reacting of grout constituents at a close and predetermined location with respect to the crack or crevice requiring repair is a useful and desirable device.
2. Description of Prior Art
Chemical grout injectors that are placed within long holes at a predetermined location away from a crack or crevice where they are used for the mixing (reacting) of grout constituents prior to injection of the grout into the crack or crevice are not hereinbefore known. Means for reacting grout at the surface of a long hole and thereafter pumping the mixture into a crack or crevice are known.
Means of pumping grout components separately into a long hole through an inner and an outer pair of grout pipes arranged in a coaxial manner and into a mixing chamber that is located at the end thereof are known. The use of coaxial grout pipes and a mixing chamber does not, however, ensure the complete reacting together of grout components, especially in the presence of a pervasive flow. Coaxial grout pipes also tend to be difficult to extract from a long hole following usage.
While the structural arrangements of other grout injection devices may, at first appearance, have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices.